The present invention relates to a heat treating basket comprising a closed or grate-shaped bottom containing upright posts with end pins integrally formed with rims and a frame resting on said posts and undetachably fixed thereto via flexible eye connections through which the pins protrude. A lug prevents the eye connection from sliding off the pins.
Heat treating baskets for the passage of material through annealing furnaces and for quenching hot material in a quenching bath are subjected to high temperature fluctuations and local differences in temperatures so that they suffer from high thermal stress, with the maximum thermal stress occurring at the frame which forms the upper rim of the heat treating basket.
In a known heat treating basket of the above mentioned type (German laid open patent application No. 28 17 718), the bottom together with the upright posts integrally formed thereto is a casting of one piece. The frame produced separately and seated in grooves at the upper ends of the posts is fixed to the posts by means of eyes or small framings which project downwardly from outside the frame to engage the lugs of the posts. When the frame is manufactured, only two bars are cast for each eye, the third bar closing the eye being applied later by welding to form the final element after the frame has been set on the ends of the posts. Due to the welding of the final elements, two welding spots at each eye and, furthermore, foreign material for the final element are required, with a resultant high expenditure in manual finish and production costs.
Accordingly, it is the object of the present invention to provide an improved heat treating basket of the foregoing type with simplified manufacturing techniques.
The problem is solved, according to the present invention, in that the eyes are integrally cast to the posts or to the frame and are aligned horizontally and the lugs are welded to the vertically extending pins.
In the heat treating basket of the present invention, the eyes are not completed by a final element in a later manufacturing step, but they are integrally formed to the bottom or frame during the casting step. When the frame is assembled to the ends of the posts of the bottom, the vertical pins are inserted into the horizontal eyes. Subsequently, by welding the lugs to the pin ends protruding through the eyes, the system is locked. One sole welding operation is necessary only to lock each eye connection. Preferably, the lugs consist of welding spots produced by using a welding material. No foreign material is needed in addition to the welding material, and the welding spots may be simply realized by selectively applying a welding electrode to the pins. The welding spots are spaced from the eye which should not be clamped so as to maintain the expansion mobility of the eye connection.
Preferably, the eyes are integrally formed to the frame, while inside portions of the post are provided with horizontal bases for supporting the frame which, towards the basket inside, are not limited by upright elements, thus allowing frame movements relative to the bottom or to the posts. Further, the inside of the frame is substantially flush with the inner post boundaries so that a wire grid mounted in the heat treating basket cannot be deflected at the transition between the posts and the frame.
The upper frame which may be made in one piece suitably consists of separate frame bars. In such a case, the latter may move and expand themselves independently from one another. Further, it is easier to produce the frame bars in separate casing molds than as a single-part frame. According to a preferred further embodiment of the invention, the posts at the corners of the bottom traverse two eyes of the two adjacent frame posts, with the two eyes being arranged at different heights. This permits, in case of a multipart frame, a simple corner connection design.
The heat treating basket of the present invention is not only favorably characterized by a simple construction but also by the fact that it can be stacked and displayed on the furnace floor. The play in all directions and the expansion mobility between bottom and frame are ensured by the eye connections which are provided.